<?php
// vim: foldmethod=marker

/* Generic exception class
 */
class OAuthException extends Exception {
	// pass
}

class OAuthConsumer {
	public $key;
	public $secret;

	function __construct($key, $secret, $callback_url=NULL) {
		$this->key = $key;
		$this->secret = $secret;
		$this->callback_url = $callback_url;
	}

	function __toString() {
		return "OAuthConsumer[key=$this->key,secret=$this->secret]";
	}
}

class OAuthToken {
	// access tokens and request tokens
	public $key;
	public $secret;

	/**
	* key = the token
	* secret = the token secret
	*/
	function __construct($key, $secret) {
		$this->key = $key;
		$this->secret = $secret;
	}

	/**
	* generates the basic string serialization of a token that a server
	* would respond to request_token and access_token calls with
	*/
	function to_string() {
		return "oauth_token=" .
				OAuthUtil::urlencode_rfc3986($this->key) .
				"&oauth_token_secret=" .
				OAuthUtil::urlencode_rfc3986($this->secret);
	}

	function __toString() {
		return $this->to_string();
	}
}

/**
 * A class for implementing a Signature Method
 * See section 9 ("Signing Requests") in the spec
 */
abstract class OAuthSignatureMethod {
/**
* Needs to return the name of the Signature Method (ie HMAC-SHA1)
* @return string
*/
abstract public function get_name();

/**
* Build up the signature
* NOTE: The output of this function MUST NOT be urlencoded.
* the encoding is handled in OAuthRequest when the final
* request is serialized
* @param OAuthRequest $request
* @param OAuthConsumer $consumer
* @param OAuthToken $token
* @return string
*/
abstract public function build_signature($request, $consumer, $token);

/**
* Verifies that a given signature is correct
* @param OAuthRequest $request
* @param OAuthConsumer $consumer
* @param OAuthToken $token
* @param string $signature
* @return bool
*/
public function check_signature($request, $consumer, $token, $signature) {
	$built = $this->build_signature($request, $consumer, $token);
		return $built == $signature;
	}
}

/**
 * The HMAC-SHA1 signature method uses the HMAC-SHA1 signature algorithm as defined in [RFC2104]
 * where the Signature Base String is the text and the key is the concatenated values (each first
 * encoded per Parameter Encoding) of the Consumer Secret and Token Secret, separated by an '&'
 * character (ASCII code 38) even if empty.
 *   - Chapter 9.2 ("HMAC-SHA1")
 */
class OAuthSignatureMethod_HMAC_SHA1 extends OAuthSignatureMethod {
  function get_name() {
	return "HMAC-SHA1";
  }

  public function build_signature($request, $consumer, $token) {
	$base_string = $request->get_signature_base_string();
	$request->base_string = $base_string;

	$key_parts = array(
	  $consumer->secret,
	  ($token) ? $token->secret : ""
	);

	$key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
	$key = implode('&', $key_parts);

	return base64_encode(hash_hmac('sha1', $base_string, $key, true));
  }
}

/**
 * The PLAINTEXT method does not provide any security protection and SHOULD only be used
 * over a secure channel such as HTTPS. It does not use the Signature Base String.
 *   - Chapter 9.4 ("PLAINTEXT")
 */
class OAuthSignatureMethod_PLAINTEXT extends OAuthSignatureMethod {
  public function get_name() {
	return "PLAINTEXT";
  }

  /**
   * oauth_signature is set to the concatenated encoded values of the Consumer Secret and
   * Token Secret, separated by a '&' character (ASCII code 38), even if either secret is
   * empty. The result MUST be encoded again.
   *   - Chapter 9.4.1 ("Generating Signatures")
   *
   * Please note that the second encoding MUST NOT happen in the SignatureMethod, as
   * OAuthRequest handles this!
   */
  public function build_signature($request, $consumer, $token) {
	$key_parts = array(
	  $consumer->secret,
	  ($token) ? $token->secret : ""
	);

	$key_parts = OAuthUtil::urlencode_rfc3986($key_parts);
	$key = implode('&', $key_parts);
	$request->base_string = $key;

	return $key;
  }
}

/**
 * The RSA-SHA1 signature method uses the RSASSA-PKCS1-v1_5 signature algorithm as defined in
 * [RFC3447] section 8.2 (more simply known as PKCS#1), using SHA-1 as the hash function for
 * EMSA-PKCS1-v1_5. It is assumed that the Consumer has provided its RSA public key in a
 * verified way to the Service Provider, in a manner which is beyond the scope of this
 * specification.
 *   - Chapter 9.3 ("RSA-SHA1")
 */
abstract class OAuthSignatureMethod_RSA_SHA1 extends OAuthSignatureMethod {
  public function get_name() {
	return "RSA-SHA1";
  }

  // Up to the SP to implement this lookup of keys. Possible ideas are:
  // (1) do a lookup in a table of trusted certs keyed off of consumer
  // (2) fetch via http using a url provided by the requester
  // (3) some sort of specific discovery code based on request
  //
  // Either way should return a string representation of the certificate
  protected abstract function fetch_public_cert(&$request);

  // Up to the SP to implement this lookup of keys. Possible ideas are:
  // (1) do a lookup in a table of trusted certs keyed off of consumer
  //
  // Either way should return a string representation of the certificate
  protected abstract function fetch_private_cert(&$request);

  public function build_signature($request, $consumer, $token) {
	$base_string = $request->get_signature_base_string();
	$request->base_string = $base_string;

	// Fetch the private key cert based on the request
	$cert = $this->fetch_private_cert($request);

	// Pull the private key ID from the certificate
	$privatekeyid = openssl_get_privatekey($cert);

	// Sign using the key
	$ok = openssl_sign($base_string, $signature, $privatekeyid);

	// Release the key resource
	openssl_free_key($privatekeyid);

	return base64_encode($signature);
  }

  public function check_signature($request, $consumer, $token, $signature) {
	$decoded_sig = base64_decode($signature);

	$base_string = $request->get_signature_base_string();

	// Fetch the public key cert based on the request
	$cert = $this->fetch_public_cert($request);

	// Pull the public key ID from the certificate
	$publickeyid = openssl_get_publickey($cert);

	// Check the computed signature against the one passed in the query
	$ok = openssl_verify($base_string, $decoded_sig, $publickeyid);

	// Release the key resource
	openssl_free_key($publickeyid);

	return $ok == 1;
  }
}

class OAuthRequest {
  private $parameters;
  private $http_method;
  private $http_url;
  // for debug purposes
  public $base_string;
  public static $version = '1.0';
  public static $POST_INPUT = 'php://input';

  function __construct($http_method, $http_url, $parameters=NULL) {
	@$parameters or $parameters = array();
	$parameters = array_merge( OAuthUtil::parse_parameters(parse_url($http_url, PHP_URL_QUERY)), $parameters);
	$this->parameters = $parameters;
	$this->http_method = $http_method;
	$this->http_url = $http_url;
  }


  /**
   * attempt to build up a request from what was passed to the server
   */
  public static function from_request($http_method=NULL, $http_url=NULL, $parameters=NULL) {
	$scheme = (!isset($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on")
			  ? 'http'
			  : 'https';
	@$http_url or $http_url = $scheme .
							  '://' . $_SERVER['HTTP_HOST'] .
							  ':' .
							  $_SERVER['SERVER_PORT'] .
							  $_SERVER['REQUEST_URI'];
	@$http_method or $http_method = $_SERVER['REQUEST_METHOD'];

	// We weren't handed any parameters, so let's find the ones relevant to
	// this request.
	// If you run XML-RPC or similar you should use this to provide your own
	// parsed parameter-list
	if (!$parameters) {
	  // Find request headers
	  $request_headers = OAuthUtil::get_headers();

	  // Parse the query-string to find GET parameters
	  $parameters = OAuthUtil::parse_parameters($_SERVER['QUERY_STRING']);

	  // It's a POST request of the proper content-type, so parse POST
	  // parameters and add those overriding any duplicates from GET
	  if ($http_method == "POST"
		  && @strstr($request_headers["Content-Type"],
					 "application/x-www-form-urlencoded")
		  ) {
		$post_data = OAuthUtil::parse_parameters(
		  file_get_contents(self::$POST_INPUT)
		);
		$parameters = array_merge($parameters, $post_data);
	  }

	  // We have a Authorization-header with OAuth data. Parse the header
	  // and add those overriding any duplicates from GET or POST
	  if (@substr($request_headers['Authorization'], 0, 6) == "OAuth ") {
		$header_parameters = OAuthUtil::split_header(
		  $request_headers['Authorization']
		);
		$parameters = array_merge($parameters, $header_parameters);
	  }

	}

	return new OAuthRequest($http_method, $http_url, $parameters);
  }

  /**
   * pretty much a helper function to set up the request
   */
  public static function from_consumer_and_token($consumer, $token, $http_method, $http_url, $parameters=NULL) {
	@$parameters or $parameters = array();
	$defaults = array("oauth_version" => OAuthRequest::$version,
					  "oauth_nonce" => OAuthRequest::generate_nonce(),
					  "oauth_timestamp" => OAuthRequest::generate_timestamp(),
					  "oauth_consumer_key" => $consumer->key);
	if ($token)
	  $defaults['oauth_token'] = $token->key;

	$parameters = array_merge($defaults, $parameters);

	return new OAuthRequest($http_method, $http_url, $parameters);
  }

  public function set_parameter($name, $value, $allow_duplicates = true) {
	if ($allow_duplicates && isset($this->parameters[$name])) {
	  // We have already added parameter(s) with this name, so add to the list
	  if (is_scalar($this->parameters[$name])) {
		// This is the first duplicate, so transform scalar (string)
		// into an array so we can add the duplicates
		$this->parameters[$name] = array($this->parameters[$name]);
	  }

	  $this->parameters[$name][] = $value;
	} else {
	  $this->parameters[$name] = $value;
	}
  }

  public function get_parameter($name) {
	return isset($this->parameters[$name]) ? $this->parameters[$name] : null;
  }

  public function get_parameters() {
	return $this->parameters;
  }

  public function unset_parameter($name) {
	unset($this->parameters[$name]);
  }

  /**
   * The request parameters, sorted and concatenated into a normalized string.
   * @return string
   */
  public function get_signable_parameters() {
	// Grab all parameters
	$params = $this->parameters;

	// Remove oauth_signature if present
	// Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
	if (isset($params['oauth_signature'])) {
	  unset($params['oauth_signature']);
	}

	return OAuthUtil::build_http_query($params);
  }

  /**
   * Returns the base string of this request
   *
   * The base string defined as the method, the url
   * and the parameters (normalized), each urlencoded
   * and the concated with &.
   */
  public function get_signature_base_string() {
	$parts = array(
	  $this->get_normalized_http_method(),
	  $this->get_normalized_http_url(),
	  $this->get_signable_parameters()
	);

	$parts = OAuthUtil::urlencode_rfc3986($parts);

	return implode('&', $parts);
  }

  /**
   * just uppercases the http method
   */
  public function get_normalized_http_method() {
	return strtoupper($this->http_method);
  }

  /**
   * parses the url and rebuilds it to be
   * scheme://host/path
   */
  public function get_normalized_http_url() {
	$parts = parse_url($this->http_url);

	$port = @$parts['port'];
	$scheme = $parts['scheme'];
	$host = $parts['host'];
	$path = @$parts['path'];

	$port or $port = ($scheme == 'https') ? '443' : '80';

	if (($scheme == 'https' && $port != '443')
		|| ($scheme == 'http' && $port != '80')) {
	  $host = "$host:$port";
	}
	return "$scheme://$host$path";
  }

  /**
   * builds a url usable for a GET request
   */
  public function to_url() {
	$post_data = $this->to_postdata();
	$out = $this->get_normalized_http_url();
	if ($post_data) {
	  $out .= '?'.$post_data;
	}
	return $out;
  }

  /**
   * builds the data one would send in a POST request
   */
  public function to_postdata() {
	return OAuthUtil::build_http_query($this->parameters);
  }

  /**
   * builds the Authorization: header
   */
  public function to_header($realm=null) {
	$first = true;
	if($realm) {
	  $out = 'Authorization: OAuth realm="' . OAuthUtil::urlencode_rfc3986($realm) . '"';
	  $first = false;
	} else
	  $out = 'Authorization: OAuth';

	$total = array();
	foreach ($this->parameters as $k => $v) {
	  if (substr($k, 0, 5) != "oauth") continue;
	  if (is_array($v)) {
		throw new OAuthException('Arrays not supported in headers');
	  }
	  $out .= ($first) ? ' ' : ',';
	  $out .= OAuthUtil::urlencode_rfc3986($k) .
			  '="' .
			  OAuthUtil::urlencode_rfc3986($v) .
			  '"';
	  $first = false;
	}
	return $out;
  }

  public function __toString() {
	return $this->to_url();
  }


  public function sign_request($signature_method, $consumer, $token) {
	$this->set_parameter(
	  "oauth_signature_method",
	  $signature_method->get_name(),
	  false
	);
	$signature = $this->build_signature($signature_method, $consumer, $token);
	$this->set_parameter("oauth_signature", $signature, false);
  }

  public function build_signature($signature_method, $consumer, $token) {
	$signature = $signature_method->build_signature($this, $consumer, $token);
	return $signature;
  }

  /**
   * util function: current timestamp
   */
  private static function generate_timestamp() {
	return time();
  }

  /**
   * util function: current nonce
   */
  private static function generate_nonce() {
	$mt = microtime();
	$rand = mt_rand();

	return md5($mt . $rand); // md5s look nicer than numbers
  }
}

class OAuthServer {
  protected $timestamp_threshold = 300; // in seconds, five minutes
  protected $version = '1.0';			 // hi blaine
  protected $signature_methods = array();

  protected $data_store;

  function __construct($data_store) {
	$this->data_store = $data_store;
  }

  public function add_signature_method($signature_method) {
	$this->signature_methods[$signature_method->get_name()] =
	  $signature_method;
  }

  // high level functions

  /**
   * process a request_token request
   * returns the request token on success
   */
  public function fetch_request_token(&$request) {
	$this->get_version($request);

	$consumer = $this->get_consumer($request);

	// no token required for the initial token request
	$token = NULL;

	$this->check_signature($request, $consumer, $token);

	// Rev A change
	$callback = $request->get_parameter('oauth_callback');
	$new_token = $this->data_store->new_request_token($consumer, $callback);

	return $new_token;
  }

  /**
   * process an access_token request
   * returns the access token on success
   */
  public function fetch_access_token(&$request) {
	$this->get_version($request);

	$consumer = $this->get_consumer($request);

	// requires authorized request token
	$token = $this->get_token($request, $consumer, "request");

	$this->check_signature($request, $consumer, $token);

	// Rev A change
	$verifier = $request->get_parameter('oauth_verifier');
	$new_token = $this->data_store->new_access_token($token, $consumer, $verifier);

	return $new_token;
  }

  /**
   * verify an api call, checks all the parameters
   */
  public function verify_request(&$request) {
	$this->get_version($request);
	$consumer = $this->get_consumer($request);
	$token = $this->get_token($request, $consumer, "access");
	$this->check_signature($request, $consumer, $token);
	return array($consumer, $token);
  }

  // Internals from here
  /**
   * version 1
   */
  private function get_version(&$request) {
	$version = $request->get_parameter("oauth_version");
	if (!$version) {
	  // Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present.
	  // Chapter 7.0 ("Accessing Protected Ressources")
	  $version = '1.0';
	}
	if ($version !== $this->version) {
	  throw new OAuthException("OAuth version '$version' not supported");
	}
	return $version;
  }

  /**
   * figure out the signature with some defaults
   */
  private function get_signature_method(&$request) {
	$signature_method =
		@$request->get_parameter("oauth_signature_method");

	if (!$signature_method) {
	  // According to chapter 7 ("Accessing Protected Ressources") the signature-method
	  // parameter is required, and we can't just fallback to PLAINTEXT
	  throw new OAuthException('No signature method parameter. This parameter is required');
	}

	if (!in_array($signature_method,
				  array_keys($this->signature_methods))) {
	  throw new OAuthException(
		"Signature method '$signature_method' not supported " .
		"try one of the following: " .
		implode(", ", array_keys($this->signature_methods))
	  );
	}
	return $this->signature_methods[$signature_method];
  }

  /**
   * try to find the consumer for the provided request's consumer key
   */
  private function get_consumer(&$request) {
	$consumer_key = @$request->get_parameter("oauth_consumer_key");
	if (!$consumer_key) {
	  throw new OAuthException("Invalid consumer key");
	}

	$consumer = $this->data_store->lookup_consumer($consumer_key);
	if (!$consumer) {
	  throw new OAuthException("Invalid consumer");
	}

	return $consumer;
  }

  /**
   * try to find the token for the provided request's token key
   */
  private function get_token(&$request, $consumer, $token_type="access") {
	$token_field = @$request->get_parameter('oauth_token');
	$token = $this->data_store->lookup_token(
	  $consumer, $token_type, $token_field
	);
	if (!$token) {
	  throw new OAuthException("Invalid $token_type token: $token_field");
	}
	return $token;
  }

  /**
   * all-in-one function to check the signature on a request
   * should guess the signature method appropriately
   */
  private function check_signature(&$request, $consumer, $token) {
	// this should probably be in a different method
	$timestamp = @$request->get_parameter('oauth_timestamp');
	$nonce = @$request->get_parameter('oauth_nonce');

	$this->check_timestamp($timestamp);
	$this->check_nonce($consumer, $token, $nonce, $timestamp);

	$signature_method = $this->get_signature_method($request);

	$signature = $request->get_parameter('oauth_signature');
	$valid_sig = $signature_method->check_signature(
	  $request,
	  $consumer,
	  $token,
	  $signature
	);

	if (!$valid_sig) {
	  throw new OAuthException("Invalid signature");
	}
  }

  /**
   * check that the timestamp is new enough
   */
  private function check_timestamp($timestamp) {
	if( ! $timestamp )
	  throw new OAuthException(
		'Missing timestamp parameter. The parameter is required'
	  );

	// verify that timestamp is recentish
	$now = time();
	if (abs($now - $timestamp) > $this->timestamp_threshold) {
	  throw new OAuthException(
		"Expired timestamp, yours $timestamp, ours $now"
	  );
	}
  }

  /**
   * check that the nonce is not repeated
   */
  private function check_nonce($consumer, $token, $nonce, $timestamp) {
	if( ! $nonce )
	  throw new OAuthException(
		'Missing nonce parameter. The parameter is required'
	  );

	// verify that the nonce is uniqueish
	$found = $this->data_store->lookup_nonce(
	  $consumer,
	  $token,
	  $nonce,
	  $timestamp
	);
	if ($found) {
	  throw new OAuthException("Nonce already used: $nonce");
	}
  }

}

class OAuthDataStore {
  function lookup_consumer($consumer_key) {
	// implement me
  }

  function lookup_token($consumer, $token_type, $token) {
	// implement me
  }

  function lookup_nonce($consumer, $token, $nonce, $timestamp) {
	// implement me
  }

  function new_request_token($consumer, $callback = null) {
	// return a new token attached to this consumer
  }

  function new_access_token($token, $consumer, $verifier = null) {
	// return a new access token attached to this consumer
	// for the user associated with this token if the request token
	// is authorized
	// should also invalidate the request token
  }

}

class OAuthUtil {
  public static function urlencode_rfc3986($input) {
  if (is_array($input)) {
	return array_map(array('OAuthUtil', 'urlencode_rfc3986'), $input);
  } else if (is_scalar($input)) {
	return str_replace(
	  '+',
	  ' ',
	  str_replace('%7E', '~', rawurlencode($input))
	);
  } else {
	return '';
  }
}


  // This decode function isn't taking into consideration the above
  // modifications to the encoding process. However, this method doesn't
  // seem to be used anywhere so leaving it as is.
  public static function urldecode_rfc3986($string) {
	return urldecode($string);
  }

  // Utility function for turning the Authorization: header into
  // parameters, has to do some unescaping
  // Can filter out any non-oauth parameters if needed (default behaviour)
  public static function split_header($header, $only_allow_oauth_parameters = true) {
	$pattern = '/(([-_a-z]*)=("([^"]*)"|([^,]*)),?)/';
	$offset = 0;
	$params = array();
	while (preg_match($pattern, $header, $matches, PREG_OFFSET_CAPTURE, $offset) > 0) {
	  $match = $matches[0];
	  $header_name = $matches[2][0];
	  $header_content = (isset($matches[5])) ? $matches[5][0] : $matches[4][0];
	  if (preg_match('/^oauth_/', $header_name) || !$only_allow_oauth_parameters) {
		$params[$header_name] = OAuthUtil::urldecode_rfc3986($header_content);
	  }
	  $offset = $match[1] + strlen($match[0]);
	}

	if (isset($params['realm'])) {
	  unset($params['realm']);
	}

	return $params;
  }

  // helper to try to sort out headers for people who aren't running apache
  public static function get_headers() {
	if (function_exists('apache_request_headers')) {
	  // we need this to get the actual Authorization: header
	  // because apache tends to tell us it doesn't exist
	  $headers = apache_request_headers();

	  // sanitize the output of apache_request_headers because
	  // we always want the keys to be Cased-Like-This and arh()
	  // returns the headers in the same case as they are in the
	  // request
	  $out = array();
	  foreach( $headers AS $key => $value ) {
		$key = str_replace(
			" ",
			"-",
			ucwords(strtolower(str_replace("-", " ", $key)))
		  );
		$out[$key] = $value;
	  }
	} else {
	  // otherwise we don't have apache and are just going to have to hope
	  // that $_SERVER actually contains what we need
	  $out = array();
	  if( isset($_SERVER['CONTENT_TYPE']) )
		$out['Content-Type'] = $_SERVER['CONTENT_TYPE'];
	  if( isset($_ENV['CONTENT_TYPE']) )
		$out['Content-Type'] = $_ENV['CONTENT_TYPE'];

	  foreach ($_SERVER as $key => $value) {
		if (substr($key, 0, 5) == "HTTP_") {
		  // this is chaos, basically it is just there to capitalize the first
		  // letter of every word that is not an initial HTTP and strip HTTP
		  // code from przemek
		  $key = str_replace(
			" ",
			"-",
			ucwords(strtolower(str_replace("_", " ", substr($key, 5))))
		  );
		  $out[$key] = $value;
		}
	  }
	}
	return $out;
  }

  // This function takes a input like a=b&a=c&d=e and returns the parsed
  // parameters like this
  // array('a' => array('b','c'), 'd' => 'e')
  public static function parse_parameters( $input ) {
	if (!isset($input) || !$input) return array();

	$pairs = explode('&', $input);

	$parsed_parameters = array();
	foreach ($pairs as $pair) {
	  $split = explode('=', $pair, 2);
	  $parameter = OAuthUtil::urldecode_rfc3986($split[0]);
	  $value = isset($split[1]) ? OAuthUtil::urldecode_rfc3986($split[1]) : '';

	  if (isset($parsed_parameters[$parameter])) {
		// We have already recieved parameter(s) with this name, so add to the list
		// of parameters with this name

		if (is_scalar($parsed_parameters[$parameter])) {
		  // This is the first duplicate, so transform scalar (string) into an array
		  // so we can add the duplicates
		  $parsed_parameters[$parameter] = array($parsed_parameters[$parameter]);
		}

		$parsed_parameters[$parameter][] = $value;
	  } else {
		$parsed_parameters[$parameter] = $value;
	  }
	}
	return $parsed_parameters;
  }

  public static function build_http_query($params) {
	if (!$params) return '';

	// Urlencode both keys and values
	$keys = OAuthUtil::urlencode_rfc3986(array_keys($params));
	$values = OAuthUtil::urlencode_rfc3986(array_values($params));
	$params = array_combine($keys, $values);

	// Parameters are sorted by name, using lexicographical byte value ordering.
	// Ref: Spec: 9.1.1 (1)
	uksort($params, 'strcmp');

	$pairs = array();
	foreach ($params as $parameter => $value) {
	  if (is_array($value)) {
		// If two or more parameters share the same name, they are sorted by their value
		// Ref: Spec: 9.1.1 (1)
		natsort($value);
		foreach ($value as $duplicate_value) {
		  $pairs[] = $parameter . '=' . $duplicate_value;
		}
	  } else {
		$pairs[] = $parameter . '=' . $value;
	  }
	}
	// For each parameter, the name is separated from the corresponding value by an '=' character (ASCII code 61)
	// Each name-value pair is separated by an '&' character (ASCII code 38)
	return implode('&', $pairs);
  }
}
